Terms And Definitions - Siemens SITRANS F Additional Operating Instructions

SITRANS FX330

1.5 Terms and definitions

Term Description
DC Diagnostic Coverage of dangerous failures
EUC Equipment Under Control
Firmware Software embedded in the device
FIT
Failure In Time (1x10
FMEDA Failure Modes, Effects and Diagnostics Analysis
FRT Fault Response Time (diagnostic test interval + Fault Reaction Time)
HFT Hardware Fault Tolerance
I/O Input / output
λ
Rate for dangerous detected failure
DD
λ
Rate for dangerous undetected failure
DU
λ
Rate for safe detected failure
SD
λ
Rate for safe undetected failure
SU
MTBF Mean Time Between Failures
MTTF Mean Time To Failure
MTTR Mean Time To Repair
MTR Mean Time To Restoration
PFD Average Probability of Failure on Demand
AVG
PFH Probability of a dangerous Failure per Hour
PTC Proof Test Coverage
SFF Safe Failure Fraction
SIL Safety Integrity Level
SIS Safety Instrumented Systems
Systematic Measure (expressed on a scale of SC 1 to SC 4) of the confidence that the systematic safety integrity of an
Capability element meets the requirements of the specified SIL, in respect of the specified element safety function,
when the element is applied in accordance with the instructions.
Type A "Non-complex" system (all failure modes are well defined). For more data, refer to subsection 7.4.3.1.2 of
system IEC 61508-2.
Type B "Complex" system (all failure modes are not well defined). For more data, refer to subsection 7.4.3.1.2 of
system IEC 61508-2.
T Proof Test Interval
Proof
T Time to Repair
Repair
T Internal Diagnostics Test Interval
Test
1oo1 1 out of 1 channel architecture (single architecture performs the safety function)
1oo1D 1 out of 1 channel architecture with diagnostics
10/2017 - A5E40875009-AB EN
-9
failures per hour)
www.siemens.com/flow
INTRODUCTION
1
7